Variable air volume control apparatus

ABSTRACT

The present invention relates to a variable air volume control apparatus capable of effectively reducing air overflow concentrated at one side due to a damper blade biased according to an open angle of the damper blade, thereby precisely adjusting the air volume. The variable air volume control apparatus includes a damper blade disposed rotatably inside the duct to open or close an air flow path and an actuator for rotating the damper blade. The apparatus also includes means for dividing the air flow path inside the duct at the air inlet side into an upper region and a lower region and exerting resistance to the air flow between the means and the biased damper blade. The invention effectively suppresses the air overflow occurring at high opening ratio of the damper blade with simple structural improvements, thereby accurately and precisely adjusting the air volume.

CLAIM OF PRIORITY

This application claims the benefit of Korean Patent Application No. 2006-21949 filed on Mar. 8, 2006, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a variable air volume control apparatus for automatically adjusting the volume of air supplied indoors, according to the temperature change therein. More particularly, the invention relates to a variable air volume control apparatus having an air flow path dividing means for dividing an air flow path of a duct into an upper and lower regions to exert resistance to air flow between a damper blade and the air flow path dividing means, effectively suppressing air overflow with the damper blade biased at high opening ratio, thereby precisely and accurately adjusting the volume of air.

2. Description of the Related Art

In general, an automatic control system of a building is equipped with a variable air volume control apparatus for varying the volume of air from the outside in order to maintain the room temperature by conditioning air inside the building.

FIG. 1 illustrates a conventional variable air volume control apparatus.

The conventional variable air volume control apparatus 200 is installed inside a duct 210 through which air from the outside is introduced. The variable air volume control apparatus 200 includes a flow sensor 220 for sensing the volume of air introduced from the outside, a damper blade 230 for adjusting the volume of air introduced from the outside to the inside, and an actuator 240 for rotating the damper blade 230.

Also, the conventional variable air volume control apparatus 200 includes a room thermostat 250 for detecting and setting the temperature indoors and a controller 260 for controlling the operation of the variable air volume control apparatus 200.

The flow sensor 220, the actuator 240 and the room thermostat 250 are electrically connected to the controller 260 to thereby be controlled.

The above variable air volume control apparatus 200 controls the volume of air through a following process.

The room thermostat 250 installed indoors senses the room temperature, and the information thereof, e.g. a signal is sent to the controller 260. Then, the controller 260 computes the information and the currently set temperature to calculate the air volume needed, thereby transmitting a signal for the opening angle corresponding to the air volume needed to the operational devices such as a motor or the actuator 240 to be operated accordingly.

In addition, the above variable air volume control apparatus 200 measures the volume of air at an inlet side by an air volume measurement device such as an anemometer or a differential pressure sensor installed at the air inlet side and sends the corresponding information (signal) to the controller 260. Then, the controller 260 receives and processes the information (signal) from the air volume measurement device to rotate a shaft 232 of the operational device as much as the excessive or deficient amount of air volume to adjust the angle of the damper blade 230, thereby maintaining the air volume in accordance with the information from the room thermostat 250.

However, the conventional variable air volume control apparatus 200 shown in FIG. 1 entails great imbalance between the opening ratio and the open area ratio corresponding to the open angle of the damper blade 230, air overflow, and friction between air flow and an inner surface of the duct 210. Thus, the open area ratio and the volume of air flowing through the duct in accordance with the opening ratio of the damper blade 230 is not in direct proportion to each other. Therefore, the air volume change ratio and the open area ratio are represented in distorted curves rather than in lines, as shown in FIG. 2.

FIG. 2 is a graph showing characteristics of the conventional variable air volume control apparatus such as the open area ratio and the air volume change ratio with respect to the opening ratio of the damper blade 230.

Characteristically most ideal for the above variable air volume control apparatus 200 is to have the open area ratio and the air volume change ratio in direct proportion to the opening ratio. Such directly proportional relationship is most desirable because it enables the controller 260 of the variable air volume control apparatus 200 to adjust the open angle as desired through the actuator 240 and the damper blade 230, thereby precisely and accurately adjusting the volume of air.

As shown in FIG. 2, with the conventional variable air volume control apparatus 200, the open area ratio as represented by curve (a) in FIG. 2 deviates greatly from line (c) directly proportional to the opening ratio of the damper blade 230.

The reason for this is because, as shown in FIG. 1, supposing that the diameter of the damper blade 230 or the diameter D of the duct 210 is 1 and the damper blade 230 is rotated in an arbitrary angle θ, the opened area created by the end portion of the damper blade 230 separated from an inner surface of the duct 210, i.e., the area through which the air can flow corresponds to a cosine function of 1-cos θ.

The area corresponding to the cosine function of 1-cos θ applies to the entire range from the vertical position of the damper blade 230 to completely block the air flow path, i.e., when θ is 0° to the horizontal position of the damper blade 230 to completely open the air flow path, i.e., when θ is 90°.

As shown by curve (b) in FIG. 2, at a low opening ratio (0% to 33%) of the damper blade 30 rotated in an arbitrary angle θ, i.e., at the open angle θ of 0° to 30°, the actual air volume change ratio is lower than the ideal air volume change ratio which is in direct proportion to line (c) but substantially in proportion to the open area ratio.

On the other hand, at a high opening ratio (50% to 100%), i.e., at the open angle θ of 45° to 90°, air flow crowds into only certain portion due to the biased damper blade 230 to result in air overflow so that air flow is greater than the corresponding open area ratio is supposed to permit.

As shown by the air volume change ratio curve (b) in comparison to the open area ratio curve (a), the air volume change ratio is more excessive at greater opening ratio.

The reason for this is because, at small opening ratio (0% to 33%), i.e., at the open angle θ of 0° to 30°, the open area ratio of the damper blade 230 is smaller than the directly proportional opening ratio line (c) with the damper blade 230 opened too narrowly by a cosine function of 1-cos θ with the air flow path constricted. At such a small open angle θ, the biased damper blade 230 hinders the air flow and thus the air volume change ratio is relatively small.

However, at a high opening ratio (50% to 100%), i.e., the open angle θ of 45° to 90°, although the open area ratio of the damper blade 230 is relatively smaller than line (c) which is in direct proportion to the opening ratio, the biased damper blade 230 does not hinder the air flow. That is, as shown in FIG. 3, the air flow in the upper area of the rotation axis 230 a of the damper blade 230 is induced toward the lower area thereof at this range of opening ratio, thereby resulting in air overflow.

As a result, with respect to the opening ratio, the air volume change ratio is expressed as curve (b) in FIG. 2, which forms an “S” line deviating greatly from line (c) which is in direct proportion to the opening ratio.

Particularly, the air overflow occurring at an opening ratio of more than 50% hinders accurate control of air flow introduced indoors, which is a major reason for failing to accurately and precisely adjust the room temperature.

That is, when the opening ratio is 50% or less, the air volume change ratio is similar to the open area ratio, but is too smaller than line (c) which is in direct proportion to the opening ratio, showing that it is difficult to adjust the volume of air via manipulating the opening ratio. When the opening ratio is 50% or greater, the open area ratio is smaller than the line in direct proportion to the opening ratio whereas the air volume change ratio is much greater than the line in direct proportion to the opening ratio. Thus, the open area ratio curve (a) and the air volume change ratio curve (b) have completely different forms from each other. As a result, the user cannot adjust the air volume via adjusting the opening ratio.

Therefore, the air overflow with the conventional variable air volume control apparatus 200 must be suppressed to accurately and precisely adjust the air volume in accordance with the opening ratio.

In order to overcome such a problem, Korean Utility Model Registration No. 0376799 (entitled “Variable Air Volume Control Device”) has been proposed.

In this conventional variable air volume control apparatus, a shaft is disposed movable back and forth and connected to a guide lever of a damper actuator disposed outside the apparatus body and operated by a room thermostat. Also, a pair of symmetrical air volume control dampers are split or joined in accordance with the movement of a pair of links that are connected to an end of the shaft. And an air conduit connects between an air inlet and a first air outlet, and is connected to a mixed air outlet.

However, this structure is structurally complex, thus difficult to manufacture, and expensive. Further, it uses a guide lever in a link structure, which makes noise and the resultant air volume change ratio curve has non-linear characteristics.

A different structure from the above is disclosed in U.S. Pat. No. 5,333,835 (entitled “Electric Motor Driven Air Valve”).

In this structure, a screw shaft is rotated by a motor to thereby move a damper blade connected to the screw shaft, adjusting the volume of air flowing between the opened damper blade and the duct.

However, it is also difficult with this conventional structure to accurately adjust air volume according to the opening ratio of the damper. Further, the structure is expensive and frequently breaks down because of structural complexity.

SUMMARY OF THE INVENTION

The present invention has been made to solve the foregoing problems of the prior art and therefore an object of certain embodiments of the present invention is to provide a variable air volume control apparatus which effectively suppresses air overflow at a high opening ratio by simple structural improvements, thereby accurately and precisely adjusting air volume.

Another object of certain embodiments of the invention is to provide a variable air volume control apparatus which can yield air volume change ratio approximate to a line in direct proportion to opening ratio of a damper blade in a high opening ratio range, thereby accurately and precisely adjusting air volume.

According to an aspect of the invention for realizing the object, there is provided a variable air volume control apparatus for adjusting air flow volume in a duct comprising: a damper blade disposed rotatably in the duct to open or close an air flow path; an actuator for rotating the damper blade; and means for dividing the air flow path in the duct at an air inlet side into an upper region and a lower region with respect to a rotation axis of the damper blade, wherein resistance is exerted to an air flow between a portion of the damper blade biased toward the air inlet side and the flow path dividing means.

Preferably, the flow path dividing means comprises a separation plate disposed in a front side of the damper blade to dichotomize the duct.

Preferably, the separation plate has sealing material at an end thereof, which provides sealing between the end of the separation plate and a portion of the rotation axis of the damper blade.

Preferably, the variable air volume control apparatus according to claim 1, wherein the flow path dividing means has a diameter 0.5 to 3 times larger than that of the duct.

Preferably, the rotation axis of the damper blade and the air flow path dividing means are shifted upward or downward from the center of the duct.

Preferably, the variable air volume control apparatus further comprises a flow path blocking means for blocking an open region between an outer surface of the damper blade and the duct.

Preferably, the flow path blocking means comprises a blocking plate in a crescent shape fixed to the duct.

Preferably, the duct has a rectangular cross-section.

According to another aspect of the invention for realizing the object, there is provided a variable air volume control apparatus comprising: a damper blade disposed rotatably inside the duct to open or close an air flow path; an actuator for rotating the damper blade; means for expanding the air flow path according to an angle of the damper blade that opens or closes the duct; and an air flow path dividing means for dividing the air flow path inside the duct in an air inlet side of the damper blade into an upper region and a lower region with respect to a rotation axis of the damper blade, wherein resistance is exerted to air flow between a apportion of the damper blade biased toward the air inlet side and the flow path dividing means.

Preferably, the flow path expanding means comprises a curved surface which compensates and expands the air flow path such that the air flow path is opened in proportion to an open angle at a small open angle rather than by a function of “1-COS θ” according to an open angle of the damper blade.

Preferably, the air flow path expanding means comprises a ring structure that is installable on an inner surface of the duct, and the damper blade has a circumference the same as an inner circumference of the ring structure.

Preferably, the flow path expanding means is formed to compensate an opening area of (θ/90)-(1-COS θ) at a small open angle, where θ is an arbitrary angle in which the damper blade is opened.

Preferably, the rotation axis of the damper blade and the flow path dividing means are shifted upward or downward from the center of the duct, and the air flow path expanding means is disposed between an outer edge of the damper blade and the duct.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a view illustrating a conventional air volume control apparatus;

FIG. 2 is a graph illustrating the open area ratio and the air volume change ratio with respect to the opening ratio, obtained by the conventional variable air volume control apparatus;

FIG. 3 is a view illustrating air overflow in the conventional variable air volume control apparatus;

FIG. 4 is a configuration view illustrating a variable air volume control apparatus according to the present invention;

FIG. 5 is a sectional view illustrating the variable air volume control apparatus according to the present invention;

FIG. 6 is a view illustrating prevention of air overflow by the variable air volume control apparatus according to the present invention;

FIG. 7 is a graph representing the open area ratio and the air volume change ratio with respect to the opening ratio, obtained by the variable air volume control apparatus according to the present invention;

FIG. 8 is a view illustrating variations of the variable air volume control apparatus according to the present invention, in which the damper blade and the air flow path dividing means are shifted downward from a center of a duct;

FIG. 9 is a view illustrating variations of the air volume control apparatus according to the present invention, in which the damper blade and the air flow path dividing means shifted variously such as upward, downward, forward and backward;

FIG. 10 is a view illustrating another variation of the variable air volume control apparatus according to the present invention including both the air flow path dividing means and the air flow path expanding means; and

FIG. 11 is a graph representing the open area ratio and the air volume change ratio with respect to the opening ratio, obtained by the variable air volume control apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

As shown in FIGS. 4 and 5, the variable air volume control apparatus 1 according to the present invention includes a flow sensor 20 installed in a duct 10 to sense the volume of air introduced from the outside, a damper blade 30 for adjusting the volume of air introduced from the outside to the inside, and an actuator 40 for rotating the damper blade 30.

In addition, a room thermostat 50 is provided to detect and set room temperature, and a controller 60 is provided to control the operation of the variable air volume control apparatus 1.

The flow sensor 20, the actuator 40, and the room thermostat 50 are electrically connected to the controller 60 to thereby be controlled.

In addition, the present invention includes an air flow path dividing means 70 disposed in the front side of the damper blade 30 (hereinafter referred to as “the air inlet side”) to divide the air flow path inside the duct 10 into an upper region S1 and a lower region S2 with respect to a rotation axis 30 a of the damper blade 30.

Such an air flow path dividing means 70 exert resistance to air flow between a portion of the damper blade 30 biased toward the air inlet side and the air flow path dividing means 70.

The air flow path dividing means 70 is preferably a separation plate 72 which is disposed in the front side of the damper blade 30 to dichotomize the duct 10. A holder (not shown) can be installed on an inner surface of the duct 10 to fix the separation plate 72.

In addition, the separation plate 72 has sealing material at a proximal end thereof, which provides sealing between the proximal end of the separation plate 72 and a portion of the rotation axis of the damper blade 30.

The air flow path dividing means has a diameter at least 0.5 times that of the duct, and preferably 0.5 to 3 times that of the duct.

As shown in FIG. 6, the variable air volume control apparatus 1 with the above configuration adjusts air volume from the open angle θ of 0° where the damper blade 20 is vertically positioned to block the air flow path, to the open angle θ of 90° where the air flow path is completely opened.

In the above process, according to the variable air volume control apparatus 1 of the present invention, as the damper blade 30 is opened in an arbitrary angle θ, air flow is divided into the upper region S1 air flow and the lower region S2 air flow by the air flow path dividing means 70 disposed in the front side of the damper blade 30 to be delivered toward the damper blade 30.

With an upper portion of the damper blade 30 biased forward, the upper region S1 with the upper air flow is divided into an open flow path P1 of an upper part of the damper blade 20 and a closed space P2 enclosed by the damper blade 30 and the air flow path dividing means 70.

Air flows well in the open air flow path P1, but the air flow is blocked and affected by great resistance in the closed space P2. Therefore, the air flow is greatly restricted in the upper region S1 of the damper blade 30 in the present invention.

On the other hand, with the damper blade 30 biased backward, the air in the lower region S2 of the air flow path dividing means 70 passes well through an air flow path P3 formed between the damper blade 30 and the duct 10 and is supplied to the back of the damper blade 30.

In the above variable volume control apparatus 1 according to the present invention, the closed space P2 enclosed by the damper blade 30 and the air flow path dividing means 70 blocks the air flow from the upper region S1 to the lower region S2, exerting great resistance to the air flow in the upper region S1 of the air flow path dividing means 70, thereby effectively suppressing the air overflow at a high opening ratio (50% or more) with the air flowing over the biased damper blade 30.

Therefore, the air overflow occurring at a high opening ratio of the damper blade 30 is suppressed to prevent excessive air flow according to the present invention.

FIG. 7 is a graph illustrating the open area ratio and the air volume change ratio with respect to the opening ratio, obtained by the variable air volume control apparatus according to the present invention described above.

In the variable air volume control apparatus, the closed space P2 formed by the air flow path dividing means 70 blocks the air flow from the upper region S1 to the lower region S2, causing great resistance to the air flow in the upper region S1 of the air flow path dividing means 70, thereby effectively suppressing the air overflow at a high opening ratio (50% or more) of the damper blade 30, as shown by curve (e) in FIG. 7.

Therefore, according to the present invention, the air overflow occurring at the opening ratio of 50% or more is effectively suppressed to prevent excessive air flow.

In addition, in the present invention, the rotation axis 30 a of the damper blade and the air flow path dividing means 70 are preferably shifted upward or downward from the initial position of the rotation axis 30 a of the damper blade 30.

Such shifted structures are illustrated in FIG. 8. In the variable air volume control apparatus 1′ shown in FIG. 8, the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 are shifted downward in a predetermined distance L from a center K of the rotation axis 30 a of the damper blade 30.

Such shifted structures are useful in the variable volume control apparatus having the upper part of the damper blade 30 opened forward and the lower part of the damper blade 30 opened backward, as shown in FIG. 8.

As discussed herein, the air flows from the upper region to the lower region over the damper blade 30 to result in the air overflow at the opening ratio of 50% or more of the damper blade 30. Thus when the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 are shifted downward from the center K of the duct, the area of the closed space P2 enclosed by the damper blade 30 and the air flow path dividing means 70 is considerably increased from D/2 to D/2+L. Therefore, the resistance to the air flow is increased in the upper region of the damper blade 30, thereby more effectively suppressing the air overflow caused by the air flowing from the upper region to the lower region over the damper blade 30.

In order for the damper blade 30 to rotate in the duct 10 in such a shifted structure, the diameter of the damper blade 30 should be maximal in the portion of its rotation axis 30 a.

The variable air volume control apparatus 1′ of the present invention further includes an air flow path blocking means 80 for blocking an open region formed between an outer surface of the damper blade 30 and the duct 10. As shown in FIG. 8(b), the air flow path blocking means 80 is a blocking plate in a crescent shape, which is fixed above the damper blade 30 by screws 82, etc.

With the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 shifted downward from the center K of the duct in a predetermined distance L, the air overflow is more effectively suppressed in the structure in which the upper part of the damper blade 30 opened forward, and the lower part of the damper blade 30 opened backward.

FIG. 8 illustrates the structure in which the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 are shifted downward from the center K of the duct in a predetermined distance L, which however does not limit the present invention. Alternatively, the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 can be shifted upward from the center K of the duct.

In this case, the air flow path blocking means 80 is fixed to the duct below the damper blade 30, which more effectively suppresses the air overflow in the structure in which the upper part of the damper blade 30 opened backward and the lower part of the damper blade 30 opened forward.

Therefore, the shift distance L of the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 can be adjusted to more effectively control the air overflow occurring at high opening ratio.

FIG. 9 suggests variously shifted positions of the rotation axis 30 a of the damper blade 30 and air flow path dividing means 70.

As shown in FIG. 9, in the present invention, it is possible to shift the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 upward or downward from the center K of the duct, but also it is possible to have rotation axes K1 and K1′ which are shifted forward and backward, respectively, from the center K of the duct.

Also, it is possible to have rotation axes K2 and K2′ which are shifted forward and backward, and also upward and downward, respectively. With the rotation axis 30 a of the damper blade 30 and the air flow path dividing means 70 shifted in combination from the center K of the duct, the air flow path blocking means 80 can accordingly be fixed to the duct 10 in various positions and structures.

In addition, the present invention is applicable also to a duct 10 having a rectangular cross-section in addition to a circular cross-section.

FIG. 10 illustrates another variation of the preset invention.

The variable air volume control apparatus 1″ according to the present invention includes the damper blade 30 disposed rotatably to open or close the air flow path inside the duct 10, and the actuator 40 for rotating the damper blade 30.

Also, the variable air volume apparatus 1″ includes an air flow path expanding means 100 for expanding the air flow path in accordance with the open angle of the damper blade 30 as the damper blade 30 is opened. The air flow path expanding means 100 expands and compensates the air flow path such that the air flow path, which was opened by a function of “1-COS θ” at a small open angle, is now opened in proportion to the opening ratio.

That is, the air flow path expanding means 100 of the present invention has a curved surface 110, which compensates for an opened area of (θ/90)-(1-COS θ), and accordingly, at a low opening ratio, i.e., 0% to 30%, the damper blade is opened at an open angle of θ/90.

Here, θ is an open angle of the damper blade 30 from the closed position of the damper blade 30.

In addition, the air flow path expanding means 100 is a ring structure 112 that is installable on an inner surface of the duct 10, having an inner circumference the same as the circumference of the damper blade 30.

In addition, the ring structure 112 preferably has a circular inner periphery or alternatively, an oval inner periphery in which the horizontal diameter, i.e., the axis of the damper blade is larger than the vertical diameter thereof.

In addition, the air flow path expanding means 100 may be formed by deforming the inner side of the duct 10 or by deforming an outer side of the duct, rather than using a ring structure 112 described above.

In addition to the air flow path expanding means 100, the present invention further includes the air flow path dividing means 70 which divides the air flow path of the duct 10 at an air inlet side into an upper region S1 and a lower region S2 with respect to a rotation axis 30 a of the damper blade 30, exerting resistance to air flow between a portion of the damper blade 30 biased toward the air inlet side and the air flow path dividing means 70.

The variable air volume control apparatus 1″ having both the air flow path expanding means 100 and the air flow path dividing means 70 exhibits the open area ratio and the air volume change ratio with respect to the opening ratio as shown in FIG. 11.

The open area ratio curve (a′) obtained by the variable air volume control apparatus 1″ of the present invention is substantially more in direct proportion to the opening ratio curve (c) at a low opening ratio (0% to 30%) than the open area ratio curve (a) of the conventional variable air volume control apparatus.

As described above, when the damper blade 30 is opened in an arbitrary angle θ from the position of blocking the air flow path, for example, when the open angle θ is opened in 9° (opening ratio of 10%), the air flow path expanding means 100 expands and compensates an opened area of the air flow path by 9/90-(1-COS 9°). When the damper blade 30 is gradually opened to have an open angle θ of 27° (opening ratio of 30%), the air flow path expanding means 100 expands and compensates the air flow path by 27/90-(1-COS 27°), increasing the air volume.

As described above and shown by curve (a′) in FIG. 11, when the opening ratio of the air flow path expanding means 100 is 30% or less, i.e., the open angle θ of the damper blade 30 is 27° or less, the open area ratio is in direct proportion to the opening ratio, thereby resulting in significantly improved linear characteristics.

Therefore, when the opening ratio is from 0% to 50%, the open area ratio is in direct proportion to the opening ratio, thereby resulting in improved linear characteristics of the air volume change ratio with respect to the opening ratio. This allows more accurate and precise adjustment of the air volume.

On the other hand, when the opening ratio is 50% or more, the air volume change ratio has improved linear characteristics with respect to the opening ratio due to the air flow path dividing means 70, enabling more accurate air volume control. This is because the air flow is blocked from the upper region S1 to the lower region S2 due to the closed space P2 formed by the air flow path dividing means 70, causing resistance to the air flow in the upper region S1 of the air flow path dividing means 70. Therefore, the air overflow at a high opening ratio, i.e., 50% or more of the damper blade 30, is effectively suppressed as shown by curve (e).

Therefore, according to the variable air volume control apparatus 1″ of the present invention, the open area ratio is improved with respect to the opening ratio at the opening ratio of 50% or less of the damper blade 30 due to the air flow path expanding means 100. Thereby, the air volume change ratio with respect to the opening ratio is improved to have linear characteristics. On the other hand, at the opening ratio of 50% or more, the air overflow is effectively suppressed by the air flow path dividing means 70, thereby preventing excessive air flow.

As a result, the variable air volume control apparatus 1″ having both the air flow path expanding means 100 and the air flow path dividing means 70 according to the present invention yields the air volume change ratio curve (f) shown in the dotted line in FIG. 11. Thus, the air volume change ratio is closely approximate to the opening ratio curve (c) in the entire range of the opening ratio, i.e., 0% to 100%. This enables more accurate and precise air volume control in accordance with the opening ratio.

According to certain embodiments of the present invention set forth above, the air overflow occurring at high opening ratio of the damper blade is effectively suppressed through simple structural improvements, thereby enabling accurate and precise air volume control.

Moreover, a certain embodiment of the present invention adjusts the air volume change ratio to be more approximate to the opening ratio of the damper blade, enabling more accurate and precise control of air volume.

Furthermore, according to a certain embodiment of the present invention, the variable air volume control apparatus has both the air flow path expanding means and the air flow path dividing means to more accurately and precisely control the air volume in proportion to the opening ratio in the entire range of the opening ratio.

The present invention has been explained and illustrated with specific embodiments. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. While the present invention has been shown and described in connection with the preferred embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A variable air volume control apparatus for adjusting air flow volume in a duct comprising: a damper blade disposed rotatably in the duct to open or close an air flow path; an actuator for rotating the damper blade; and means for dividing the air flow path in the duct at an air inlet side into an upper region and a lower region with respect to a rotation axis of the damper blade, wherein resistance is exerted to an air flow between a portion of the damper blade biased toward the air inlet side and the flow path dividing means.
 2. The variable air volume control apparatus according to claim 1, wherein the flow path dividing means comprises a separation plate disposed in a front side of the damper blade to dichotomize the duct.
 3. The variable air volume control apparatus according to claim 1, wherein the flow path dividing means has a diameter 0.5 times larger than that of the duct.
 4. The variable air volume control apparatus according to claim 2, wherein the separation plate has sealing material at an end thereof, the sealing material providing sealing between the end of the separation plate and a portion of the rotation axis of the damper blade.
 5. The variable air volume control apparatus according to claim 1, wherein the rotation axis of the damper blade and the air flow path dividing means are shifted upward or downward from the center of the duct.
 6. The variable air volume control apparatus according to claim 5, further comprising a flow path blocking means for blocking an open region between an outer surface of the damper blade and the duct.
 7. The variable air volume control apparatus according to claim 6, wherein the flow path blocking means comprises a blocking plate in a crescent shape fixed to the duct.
 8. The variable air volume control apparatus according to claim 1, wherein the duct has a rectangular cross-section.
 9. A variable air volume control apparatus comprising: a damper blade disposed rotatably inside the duct to open or close an air flow path; an actuator for rotating the damper blade; means for expanding the air flow path according to an angle of the damper blade that opens or closes the duct; and an air flow path dividing means for dividing the air flow path inside the duct in an air inlet side of the damper blade into an upper region and a lower region with respect to a rotation axis of the damper blade, wherein resistance is exerted to air flow between a apportion of the damper blade biased toward the air inlet side and the flow path dividing means.
 10. The variable air volume control apparatus according to claim 9, wherein the flow path expanding means comprises a curved surface which compensates and expands the air flow path such that the air flow path is opened in proportion to an open angle of the damper blade at a small value of open angle rather than by a function of “1-COS θ” of the open angle.
 11. The variable air volume control apparatus according to claim 10, wherein the air flow path expanding means comprises a ring structure that is installable on an inner surface of the duct, and the damper blade has a circumference the same as an inner circumference of the ring structure.
 12. The variable air volume control apparatus according to claim 10, wherein the flow path expanding means is formed to compensate an opening ratio of (θ/90)-(1-COS θ) at a small value of open angle, where θ is an arbitrary angle in which the damper blade is opened.
 13. The variable air volume control apparatus according to claim 10, wherein the rotation axis of the damper blade and the flow path dividing means are shifted upward or downward from the center of the duct, and the air flow path expanding means is disposed between an outer edge of the damper blade and the duct.
 14. The variable air volume control apparatus according to claim 9, wherein the air flow path expanding means comprises a ring structure that is installable on an inner surface of the duct, and the damper blade has a circumference the same as an inner circumference of the ring structure.
 15. The variable air volume control apparatus according to claim 9, wherein the flow path expanding means is formed to compensate an opening ratio of (θ/90)-(1-COS θ) at a small value of open angle, where θ is an arbitrary angle in which the damper blade is opened.
 16. The variable air volume control apparatus according to claim 9, wherein the rotation axis of the damper blade and the flow path dividing means are shifted upward or downward from the center of the duct, and the air flow path expanding means is disposed between an outer edge of the damper blade and the duct. 